Vehicle-to-X communication is currently at the research or pre-development stage and is undergoing a standardization process. In particular, vehicle-to-X communication can be based on the standard IEEE 802.11p. Typically, vehicle-to-X communication comprises both vehicle-to-vehicle communication as well as vehicle-to-infrastructure communication. Information can therefore be exchanged both between different vehicles and between infrastructure and vehicles. The former permits, for example, the exchange of position information and speed information between vehicles in order to avoid collisions. The latter permits, for example, the electronic notification of speed limits or traffic information.
In a vehicle-to-X communication system, both the functionality of the vehicle-to-vehicle communication as well as the vehicle-to-infrastructure communication are typically implemented. Possible receivers of messages which are emitted by the vehicle-to-X communication system can be located anywhere around the vehicle. Accordingly, it is basically advantageous if signals are irradiated at an angle of 360° around the vehicle. Ideally, an antenna which correspondingly irradiates on all sides can be used for this.
However, in many vehicles this is not always possible owing to the design or else owing to specific special equipment such as, for example, sun roofs. In such cases, two antennas can be used. In order to reduce the channel load in ranges which are covered by respective irradiation characteristics of both antennas, in such a case a communication system with transmission diversity is used. This ensures that signals are irradiated via both antennas in such a way that despite simultaneous irradiation these signals do not also give rise to problems in regions with overlapping irradiation characteristics. However, communication systems with transmission diversity are very expensive, which significantly increases the cost of the system and prevents widespread use of vehicle-to-X communication becoming established as quickly as possible, which is necessary for the technology to be successful.